Book Reviewed: Dark Matter and the Dinosaurs: The Astounding Interconnectedness of the Universe, by Lisa Randall

Did dark matter cause the demise of dinosaurs?

In this book entitled, “Dark Matter and the Dinosaurs: The Astounding Interconnectedness of the Universe,” Harvard University Professor Lisa Randall proposes a very speculative idea that the mass extinctions of dinosaurs that occurred 65 million years ago was due to an impact of a comet dislodged from its orbit around the solar system. It’s a tall claim with no experimental support, but the book offers alternative explanation for a seemingly slam-dunk debate. Her original research paper appeared in on online journal at: arxiv.org/abs/1403.0576.

The theoretical assertion is that dark matter can clump up into a thin, flat disc in the Milky Way Galaxy’s plane, and as the solar system orbits the center of the galaxy, it oscillates up and down on a regular cycle, and it would pass through the dark matter disc every 35 million years. Such an event is likely to dislodge comets orbiting the solar system and shoots directly towards earth. Though dark matter is estimated to account for 85% of total mass of the universe, these particles are not yet detected since they do not interact with the visible matter. However their presence is explained through their gravitational influence in clusters of galaxies. They also reside in spherical “halos” around galaxies. Professor Randall suggests that a fraction of dark matter also experiences a force analogous to electromagnetism, which she calls “dark light.” Through its interactions with “dark light” this weird subset of dark matter could form an invisible disk that overlaps with the visible disk of spiral arms in our Milky Way galaxy. This dark disk might have interrupted the orbit of a comet on the outer fringes of the solar system, sending it on a collision course with earth approximately about 70 million years ago. She observes that the crater record on Earth indicates nonrandom impacts at regular intervals of approximately 35 million year periodicity.

The sequence of events connecting dark matter to demise of dinosaurs is very slim: We still need to define the identity of dark matter and whether there is a pattern to comet strikes on Earth. The earth is regularly impacted by asteroids more than comets, and secondly, in the recent history of earth, giant planets like Jupiter has watched over earth like a big brother and kept earth out of harm’s way by gravitationally pulling many comets. The Comet Shoemaker–Levy 9 hit Jupiter in July 1994, and in Nov 2013, comet ISON hit sun head-on bringing its own death. Thus we have Sun and Jupiter to watch over earth. In addition, one needs to distinguish earth craters formed by comet and asteroid impacts.

Recent studies have suggested that the asteroid that hit Yucatan Peninsula 65 million years ago also intensified volcanic eruptions in the Deccan Plateau in South Asia. Volcanic eruptions became twice as intense, throwing out a deadly cocktail of sulfur dioxide and carbon dioxide. The shockwaves produced at this time shook up earth and its volcanic “plumbing systems” around the world, creating larger magma chambers that spewed out more material. This cataclysmic event also deprived oxygen in oceans thus killing thousands of aquatic species. This “combined effect” is now believed to be responsible for wiping out dinosaurs. But Professor Randall’s proposal suggest that dinosaur demise occurred 70 million years ago, thus introducing a large discrepancy between theory and factual observation. Other possible experiments to prove this hypothesis is that we need to look for the presence of such a disk in Milky Way by studying the gravitational effects on other stars in the galaxy. The recently launched Gaia telescope will map the motion of a billion stars in our galaxy, and this study may reveal the presence of dark matter disc. Professor Randall’s proposal has more questions than answers, but it is certainly a fascinating theoretical idea.